1. Field of the Invention
The present invention refers to an angular position transducer for a rotating member which preferably, but not exclusively, is the selection shaft of a type-bearing element or the driving shaft displacing the carriage of office printing machines.
2. Description of the Prior Art
Several examples of transducers are known which use a disc connected to the rotating member having on its periphery a set of active parts, and a detector which senses the progressive approach of these active parts, thus generating electrical signals which indicate the corresponding law of motion. The transducers may be of various types, e.g. optical, inductive or capacitive.
The angular position being constant, each error in the axial distance between the periphery of the disc and the detector causes a variation in the electrical signal of the detector and generates an error in the parameter to be measured. In order to minimize this inconvenience the transducers comprise a supporting structure in which the disc shaft rotates on precision bearings. The structures of the transducer is fixed directly to the rotating member support, whilst the disc shaft is connected to the rotating member by means of a decoupling joint or, alternatively, a flexible shaft. Both solutions cause an increase in the overall dimensions and cost of the rotating member-transducer combination and complications in mounting the transducer on the member itself.
Another cause of error is the variation in the electrical response due to temperature, supply voltage and other external effects.
It is therefore an object of this invention to provide a position transducer for a rotating member in which the position errors are minimized and which is also simple and economical.
Another object of this invention is to provide a position transducer using a disc which may be simply and economically connected to the member.
Another object of this invention is to provide a transducer which allows axial displacements of the rotating member without large errors in misalignment between the structure of the transducer and the axis of the rotating member.